Perplexing PLX !!**??

[jknox]

jKnox

Thanks for throwing in ......

Do you have any logs ????

I was told the capacitor was NOT necessary. As the electronics dude do you think this would have any inpact on AFR readings between OL and CL ??

I was told that the voltage reading should be 2.35 with ignition on and that as the heater element warms up it should get leaner (higher voltage ?) and when the car is started the voltage should drop. That is all the help I got from them and obviously nobody from PLX posted to this thread.


DH

Logs? Just about every drive for the last two months... What would you like to see?

As to whether or not the cap is truly needed depends upon the design of the ecm itself. I don't have a spare to disassemble (anybody got a junker?), but I'd be very surprised to find that GM doesn't have filtering of some sort on it's inputs. The question is how much and how designed? There's the possibility that somebody figured that since the egr position doesn't need a high degree of accuracy that they could shave a few pennies on the filtering there.

I look at it this way. Treat the ecm as a high impedance black box (worst case). In this instance, the wire from the controller resembles an antenna as much as anything. A small capacitor placed across that antenna is going to shunt a lot of the picked-up noise straight to ground, no matter what filtering the ecm itself has. At the same time, the input signal changes slowly enough that the capacitor will have no effect on on the desired signal.

PLX's description of what happens to the voltage matches what we see, as far as it goes - but sheesh! We could just about get that from the docs!

[jknox]

I guess, since this is a big part of the equation, I should state how mine is hooked up.

- I am simming the narrowband with mine and both analog outputs have the noise reducing capacitors connected to them and grounded at the PCM.

- the ground for the PLX is on a chassis ground that is near the PCM ground (the PCM grounds to the passenger side head)

- I did not use any wires that came with the controller, I used bigger wire for all connections.

- my controller is mounted in the battery area, against the firewall. It is amazing how cool this area stays even with the hot engine bay temps


Oh yeah, JKnox, where in the hell is Chapmansboro?

I was thinking about simming, but I started seeing people question the accuracy before I received mine. I decided to be a little extra paranoid. And it's kind of nice to be able to use the stock nb's as a sanity check - they seem to track each other halfway decently near stoich.

I wish I knew exactly where the ecm is grounded on the trucks - beefing up the grounds the way I did is admittedly a shotgun approach.

As for locating the controller under the hood, I'm not worried so much about heat as I am moisture - get a little road spray up in there with everything as exposed as it is and you can kiss your accuracy goodbye!

And unfortunately, I'm about 200 miles away from you. Chapmansboro is a wide spot in the road about 30 miles NW of Nashville. Trailer trash country is where I be!

[jknox]

do not ground the wideband heater to the HPTuners Device
the traces are not designed for the heater ground of other devices to go thru it....they are designed for just the analog output of the controller device...

That's annoying (although not surprising). I need to fish the controller back out and take some good pictures, but I'm all but certain that the power ground and the ground on the 4-pin plug are simply on the same groundplane.

I wonder if we can get anybody at plx to tell us whether or not we can run the heater ground separate - that would be the easiest solution (you'd still have display ground, but that should be less than 100ma).

Otherwise probably the best bet would be to run the signal and ground from the 4-pin to the pro interface, and then run a heavy wire from the controller's power plug to ground pin on the odbii plug. That would keep the ground loop as short as possible. Grounding the controller's power anyplace else could end up giving you a real current running in the ground between the controller and interface which would make life a whole lot more entertaining.

[Dirty Howie]

Howie, here are some of my logs per request.

You will have to use my config files because I read my wideband throught the EGR since it is installed permanently in the car. These scans are a couple of months old because I have been messing with it lately. I changed injectors, and have been messing with the 02 switching points. I also have a Z06 intake I'm getting ready to put on, so I figured I would tune it all at one time.

2000C-5

Fianally got around to this.....

I downloaded your config and looked at your log. I see in the table how your EGR voltage fluctuates. But your chart which is labeled for AFR, doesn't show any.

Your histogram shows 14.63 in all cells but that appears to be labeled the commanded AFR.

So although I'm sure you look good over at your end....from my end I don't see it


DH

[S2H]

Just an update for you guys...
did a tune today...
wideband matched narowbands..so its not an issue with our widebands....
its definately a modded issue with narrowbands
I tuned a 224 cam and it seemed to jive just fine
he had rear o2's so we moved the front ones back(no cats) and welded in a bung for my wideband...
In the rear bung the narrowbands lined up perfect with my wideband
in the front the narrowbands were quite a bit off....
so its definately a heat issue...
get the narrowbands back further where the heat is not an issue and then check your wideband vs narrowband again...
My LC1 is fine...otrher brands need to be double checked

[Dirty Howie]

Just an update for you guys...
did a tune today...
wideband matched narowbands..so its not an issue with our widebands....
its definately a modded issue with narrowbands
I tuned a 224 cam and it seemed to jive just fine
he had rear o2's so we moved the front ones back(no cats) and welded in a bung for my wideband...
In the rear bung the narrowbands lined up perfect with my wideband
in the front the narrowbands were quite a bit off....
so its definately a heat issue...
get the narrowbands back further where the heat is not an issue and then check your wideband vs narrowband again...
My LC1 is fine...otrher brands need to be double checked

Thanks for the update.....

Does it make sense (if it is a heat issue) that my WB has less error when I am running the car hot. I have noticed 15.2 instead of 15.5-6 when racing around in 3rd gear instead of cruising in D on the freeway. I posted these logs above here somewhere. Also I looked at a log from the track a couple of months ago (see below) and my AFR was even closer.

And how about the WOT. Is there any reason to doubt those AFR's. ???


DH

[5_Liter_Eater]

And how about the WOT. Is there any reason to doubt those AFR's. ???

I'm gonna say no just because I don't want to have to get a new wide band.

[S2H]

at this point I say trust your wideband

[Dirty Howie]

Well,l recently I noticed my WOT AFR going lean. I thought I might have an exhaust leak and actually found my air tube check valve not working (but this made no difference in my WB reading when replaced). Then I read the thread about the different WB's and realized that maybe my sensor has just aged quickly (its 4 months old). I consume oil (engine to be replaced) and I use TORCO which has metalic components and I track my car monthly.

So I went back and found the thread I started the day I had my WB installed:
http://www.hptuners.com/forum/showthread.php?t=10492
I was in CL at the time as I didn't even now how to put the car in OL. Below is the log if you don't want to reference the thread.

Clearly when my WB was new it read stoich at cruize in closed loop !!!!!!!!

In the last couple of days I bumped up my MAF about 5% above 7500hz to get my WOT AFR back in line......

......BUT I don't know if I am now rich or if I also have some exhaust leak issue or if my WB is indeed inacurrate now in the WOT readings too. For that matter if my WB is indeed contaminated possibly my NB's are too.

Obviously I need to get some other WB readings from a different source to see where my AFR really is.

Comments..............please !!!!!!!

[5_Liter_Eater]

Wow! The closed loop AFR from that log is spot on! I think it's worth investing in another sensor or maybe even seing if PLX will replace yours? That would be a bummer if you needed to replace the sensor every 4 months! Maybe this is where the free air calibration would be handy.

[domestic rice]

Well,l recently I noticed my WOT AFR going lean. I thought I might have an exhaust leak and actually found my air tube check valve not working (but this made no difference in my WB reading when replaced). Then I read the thread about the different WB's and realized that maybe my sensor has just aged quickly (its 4 months old). I consume oil (engine to be replaced) and I use TORCO which has metalic components and I track my car monthly.

So I went back and found the thread I started the day I had my WB installed:
http://www.hptuners.com/forum/showthread.php?t=10492
I was in CL at the time as I didn't even now how to put the car in OL. Below is the log if you don't want to reference the thread.

Clearly when my WB was new it read stoich at cruize in closed loop !!!!!!!!

In the last couple of days I bumped up my MAF about 5% above 7500hz to get my WOT AFR back in line......

......BUT I don't know if I am now rich or if I also have some exhaust leak issue or if my WB is indeed inacurrate now in the WOT readings too. For that matter if my WB is indeed contaminated possibly my NB's are too.

Obviously I need to get some other WB readings from a different source to see where my AFR really is.

Comments..............please !!!!!!!

I would say to either burrow someones w/b or make a trip to the dyno. See how your readings compare.

[VYSSLS1]

how old is your sensor?

the LSU4.2 dont last very long even with unleaded fuel, i dont use them often for this exact reason, if you are using the PCV system and sucking a little oil through the motor this will kill them very very fast, also moisture will kill them straight away so always mount the sensor pointing down in the pipe a little bit,

we can get the sensor for $75aud which is about $50usd, so just replace the sensor when you think it may not be doing what you think it is doing,

[Dirty Howie]

how old is your sensor?

the LSU4.2 dont last very long even with unleaded fuel, i dont use them often for this exact reason, if you are using the PCV system and sucking a little oil through the motor this will kill them very very fast, also moisture will kill them straight away so always mount the sensor pointing down in the pipe a little bit,

we can get the sensor for $75aud which is about $50usd, so just replace the sensor when you think it may not be doing what you think it is doing,

Mate

I have 4 catch cans ...... no oil foes thru the intake.

But I think some rings are bad as I consume oil.

My sensor is mounted in the 10'Oclock postition.

Thanks for your input.


DH

[2000C-5]

Hey Howie, have you seen this? Hmmmm............

http://www.fordmuscle.com/archives/2...tout/index.php

[Dirty Howie]

Hey Howie, have you seen this? Hmmmm............

http://www.fordmuscle.com/archives/2...tout/index.php

Thanks....saw it !!!!!!! If I get a new one it will be one that can be calibrated.

I have no idea if I can trust my WB now. I may have some exahuast or intake leaks. Had the AIR check valve replaced with a new one.

Here is recent logs.

First one is 2 days before going to the track to make sure all is OK. My WOT/PE seems to be very good....approx 1% MAF AFR error. And I did it on a hot day. Cruise cells showed typical AFR in the 15.x range.

Second log is from the track. Conditions were very hot and my commanded AFR was very low with actual error WOT/PE about 2%

Third log is the day after the track, temps still hot around here but my AFR is WAY lean. Cruise is in the 17.x range. And WOT/PE is out of site at over 8%

Even though its 80-100 degrees I don't get any pinging. The only KR is on the third log lugging uphill in D at low rpm....I could here it and downshifted to 3rd.

So I am slowly going


DH

[siastuning]

Hey Howie, have you seen this? Hmmmm............

http://www.fordmuscle.com/archives/2...tout/index.php

Hey Howie,

I just emailed you, call me if you have any more questions.

BTW here is PLX's response to that Article.

http://www.forum.plxdevices.com/viewtopic.php?t=1312

[Dirty Howie]

Hey Howie,

I just emailed you, call me if you have any more questions.

BTW here is PLX's response to that Article.

http://www.forum.plxdevices.com/viewtopic.php?t=1312

Vic

Thanks for taking the time to signup and post.....I thought you might have forgot about me

Its too bad you don't have HPT so you could view the logs. I will take some pics of the AFR tables for your viewing pleasure.

Let me go check my email .............


DH

[sixvi6-camaro]

I've been reading this thread all along and have been using my PLX hoping there would be some kind of decent solution and well regardless of reasons why the PLX is off at cruise (because of mods, heat, aliens, phase of the moon.. j/k ) I have my pass side simed and with the PLX reading that far off and no way to recal it or compensate or change anything with the PLX I'm going to dump it. I have my pass side NB simmed and although the PLX's inaccuracy at stoich doesn't to cause any driveability or tuning issues, I just hate how the LTFT are way off bank to bank. I've had an LC1 for he past couple weeks going back and forth and this weekend for sure out goes the PLX and in goes the LC1.

[Dirty Howie]

I've been reading this thread all along and have been using my PLX hoping there would be some kind of decent solution and well regardless of reasons why the PLX is off at cruise (because of mods, heat, aliens, phase of the moon.. j/k ) I have my pass side simed and with the PLX reading that far off and no way to recal it or compensate or change anything with the PLX I'm going to dump it. I have my pass side NB simmed and although the PLX's inaccuracy at stoich doesn't to cause any driveability or tuning issues, I just hate how the LTFT are way off bank to bank. I've had an LC1 for he past couple weeks going back and forth and this weekend for sure out goes the PLX and in goes the LC1.

Well please post up the results. It will be interesting to see how two different WB read in the same setup.


DH

[flea]

DH,

Check out the following link. RHS might be on to something here.

http://www.hptuners.com/forum/showthread.php?t=11527

Also,

GM Technical Service Bulletin #87-8-139

METHOD OF VERIFYING ' GOOD ELECTRICAL SYSTEM GROUND ' #87-8-139 - (04/07/1987)
VEHICLES AFFECTED: ALL MODELS

When diagnosing electronic systems for incorrect operation, it is often necessary to verify that ground circuits are good. This article is intended to clarify what is meant by the term "good ground" and the preferred tools and methods for verifying it.

A "good ground" is a ground circuit that has a resistance of zero OHMS.

Ground circuit resistance can be measured in OHMS using a digital volt OHM meter (DVOM). When using a DVOM, it must be set on the 200 OHM scale to obtain an accurate measure of the circuit resistance. Many meters have both a 200 OHM scale and a 200 K scale. The 200 K scale will not measure zero OHMS accurately. If you are not sure how the meter is to be set for the 200 OHM scale, refer to the meter operating instructions for proper settings. If the meter is an autoranging or self-scaling meter, read the meter carefully to be sure which scale it is setting itself to.

Before measuring resistance in any circuit, the resistance of the meter should be measured by touching the leads together. A meter with a good battery and leads in good condition will read less than .2 OHMS usually zero. If the leads measure anything more, an accurate measure of the circuit resistance may not be possible.

Always remember - resistance cannot be measured accurately on a "live" circuit, All current flow through a circuit must be stopped by disconnecting its power source before measuring resistance.

Ground circuit resistance can also be checked by measuring the voltage drop across the circuit with a DVOM set on, the 2 volt scale. The voltage drop will be zero across a "good ground" circuit.

Remember, fully understand a meter's functions before using it!
To add to this, a good ground for car audio applications will have a return resistance reading of 1/2 ohm or less. I have yet to have a return reading of 0 ohms. If a ground return reading cannot be made to get below 1/2 ohm by means of the "BIG 3", then it is adviseable to ground direct to the battery. Electricity is an algebra equation, what you do to one side you must do to the other. Pay as much attention to the ground wire as you do the power wire.
The BIG 3 is a great place to start for a good ground, however it is the assumed proper method of grounding. What we are talking about here is the older and wiser 4th brother to the BIG 3 (the BIG 4).
So a proper ground wire will be as follows.
- clean of residue and paint.
- secure.
- have a resistance return of 1/2 ohm or less.
- be of adequate guage to carry the return as compared to the power wire.
To simplify the measuring of the return, use your meter as described. Disconnect the - battery terminal and disconnect the ground wire from you amp. If your dmm probes are not long enough, you will need to create a jumper extension out of some primary wire or whatever wire you have handy. Measure this wire for any resistance reading and subtract it from the total.
Many installers are not aware of this nor practice this method. It takes time and time = $ so don't get all pissy if you had a professional install done and this was not checked. A poor ground connection or high resistance reading may seem trivial under no load, but once you are pounding your nice new amp and it is drawing large amounts of current, this little reading has become a monster reading that has caused many an amp to fail for no apparent reason. It may be noticeable as a extremely hot running amplifier in a short time period, poor output levels or diminishing levels and of course a blown power supply or output section in the amplifier.